Liquid-Argon Purity Demonstrator cleans up well

A large holding tank and network of filters make up the Liquid-Argon Purity Demonstrator. Photo: Terry Tope, PPD

It's been 15 months since the Liquid-Argon Purity Demonstrator filtered its first batch of liquid argon, showing for the first time that to purify it, you don't have to throw it out with the proverbial bathwater.

The demonstrator, a 30-ton tank of liquid argon connected to a purifying filter system, tests whether it's possible to remove electronegative contaminants such as water and oxygen from the liquid without having to evacuate the vessel before filling it with argon, as previous experiments have done.

Recently, the LAPD team was able to do just this, successfully purifying liquid argon at the tank's full capacity without having to first evacuate the vessel. The results are very important to a number of neutrino experiments at Fermilab: Constructing a system similar to the demonstrator means that experiments using liquid argon can forgo the often expensive task of building evacuable vessels.

One of the demonstrator's challenges is to purify liquid argon to the levels needed for experiments such as MicroBooNE and LBNE. In such experiments, neutrinos strike liquid argon nuclei, producing particles that then ionize the argon atoms. The resulting electrons drift to wire detectors, also located in the tank.

Ultra-pure argon is important for being able to detect the ionization electrons created when charged particles travel through the liquid. This is because electronegative impurities such as water and oxygen could "gobble up" the electrons, never allowing them to travel the full distance to the readout wires, which can be over 2 meters from the point of ionization, said Fermilab physicist Brian Rebel, who leads the LAPD effort.

The demonstrator’s tank is first purged with argon gas, which acts like a piston to force the atmosphere out of the tank and reduce initial contamination levels. It then circulates through the filter network. After a full cycle, the argon ends up back in the tank to start the process over.

“This is an ultra-high-purity system, but there are a lot of steps to get to that state,” said Terry Tope, lead engineer for the demonstrator design.

For the first time, the demonstrator is filtering a full load of liquid argon, Rebel said. The 30-ton tank previously contained only one-third its full capacity.
Now scientists and engineers have mastered the purification of large volumes of liquid argon and can reduce electronegative contaminants down to a concentration of about 75 parts per trillion, which is low enough to ensure a strong signal, even if the electrons have to travel more than 2 meters before detection.

Additionally, a time projection chamber, used to detect the ionization electrons, now resides in the tank. The LAPD team has recorded clear images of a cosmic ray muon's path through the argon.

Deer out of hiding

It's rare to see deer on the Fermilab grounds, let alone three out in the open. Photo: Oleksandr Borysov, Bogolyubov Institute

In Brief

Summer hiring

This year's general summer hiring program will follow the same process as 2012, which was designed to democratize the program while preserving preference given to employee-referred candidates—particularly children of employees. Please note that intern programs do not follow this process.

The laboratory benefits from employing children of employees who already know and respect laboratory culture, and employees appreciate their children's opportunity to gain work experience at Fermilab.

The following changes to the summer hiring program will be applied again in 2013:

Employees may not request candidates on personnel requisitions.

There will be no generic job postings. We will now post each job specified with individual duties and knowledge, skills and abilities (KSAs).

HR will evaluate candidates based on their responses to KSA-based screening questions.

HR will not consider candidates who do not submit responses to screening questions.

HR will refer only the top three candidates ranked for each job to the hiring manager.

If there are no employee-referred candidates available or if no employee-referred candidates meet the qualifications, then outside candidates will be considered.

Hiring managers are encouraged to submit their Summer Personnel Requisitions as soon as possible, no later than April 12. The summer employment announcement will be posted on the Employment website upon receipt of an approved Summer Personnel Requisition form. The SPR form is available via the Service Desk website. Under the "Request Things" heading, click "Summer Personnel Request." Please contact Jason Johnson (x5810) with questions regarding the summer hiring program.

Employees are encouraged to provide feedback on their experience with the new process.

Director's Corner

Projects Inc.

Fermilab Director Pier Oddone

We are in the process of re-establishing a competitive world-class scientific program after the closure of the Tevatron. This means building several projects at once while at the same time operating the largest accelerator complex in the United States and carrying out physics research across all three frontiers of particle physics. We completed our recent projects MINERvA and DECam on schedule and under budget. Also, we are committed to finishing NOvA on schedule and on budget.

While we ultimately achieve the desired outcomes, we do so with much unnecessary drama, alarming us and more importantly our funders along the way, as happened recently with the NOvA construction. This drama arises from not anticipating and addressing problems well ahead of time either during construction or in the transition to operations. We need to improve our game. In the next couple of months I will describe in these columns some of the changes we are making to manage projects in a better, more effective and transparent way.

The Dec. 4, 2012, Director's Corner highlighted some important organizational changes at Fermilab that went into effect in late 2012. With the updated structure in place, I'd like to focus this column on one of the changes: the newly formed Office of Integrated Planning and Performance Management.

IPPM emerged from what was originally the Office of Program and Project Support. Since the realignment, which also included the merging of the Quality program and ES&H, IPPM has focused on two main goals:

The development of an integrated, five-year laboratory strategic agenda—or plan—that supports the three frontiers of high-energy physics. The agenda is a living document that identifies the infrastructure projects, systems and capabilities necessary to achieve Fermilab's strategic goals. The agenda has been put through intensive scrutiny and evolution during management workshops. We will be sharing the agenda with everyone at the lab in the coming weeks.

The development of an integrated planning process that includes all essential information regarding coordination and alignment of laboratory and DOE-HEP program budgets, staff resources, skill needs and readiness of facility infrastructure and systems. This process has been used since November and is proving to be a valuable tool to ensure integration of goals, effort and priorities across the lab as our mission evolves for the future.

Also under way in IPPM is the recruitment of a program head (Carl Strawbridge has been interim head since April). The search is in progress, with a goal to fill the position this spring.

IPPM is an important element in planning and managing performance across the multiple activities of the laboratory, integrating all the necessary human, financial and technical elements. In particular, IPPM supports the execution of multiple projects now under way and in the future.

Construction Update

Electrical panels and water supply lines installed at NOvA

Lights, ventilation equipment and water lines are being installed at the NOvA Near-Detector Cavern. Photo: Cindy Arnold

Electrical panels energize the lights and ventilation equipment in the new NOvA Near-Detector Cavern. Supply air and chilled-water lines can be seen at the roof of the cavern opening prior to the installation of block walls and doors. The MINOS Detector Hall can be seen to the right.

In the News

Donald Glaser, Nobel winner in physics, dies at 86

From The New York Times, March 4, 2013

Donald A. Glaser, who won the Nobel Prize in physics in 1960 for inventing, at 25, an ingenious device called the bubble chamber to trace the paths of subatomic particles, died on Thursday at his home in Berkeley, Calif. He was 86.

His death was confirmed by his wife, Lynn.

In creating the chamber, Dr. Glaser—a restless scientist who later turned to microbiology and developing cancer therapies—proved his most renowned skeptic, Enrico Fermi, a giant of 20th-century physics, wrong.